1. Field of the Invention
The invention is in the field of drug delivery. In particular, the invention relates to drug delivery device capable of delivering one or more drugs to a patient from multiple sites of the patient's body, and coordinating the delivery of drugs at those sites. In the preferred embodiment of the invention, the delivery of drugs is accomplished by iontophoresis.
2. Description of Related Art
Iontophoresis is the application of an electrical current to transport ions through intact skin. One particularly advantageous application of iontophoresis is the non-invasive transdermal delivery of ionized drugs or other therapeutic agents into a patient. This is done by applying low levels of current to a patch placed on the patient's skin, which forces the ionized drugs contained in the patch through the patient's skin and, if desired, into his or her bloodstream for system or delivery. Because the amount of drug delivered is related to the amount of current applied, the drug delivery rate can be precisely controlled by controlling the current.
An iontophoretic drug delivery system typically includes a current source, such as a battery and current controller, and a patch. The patch includes an active reservoir and a return reservoir. The active reservoir contains the ionized drug. The return reservoir typically contains a saline gel and collects ions emanating from the patient's skin when the drug is being delivered into the patient's skin. The patch also has two electrodes, each arranged inside the active and return reservoirs to be in respective contact with the drug and saline. The anode (positive electrode) and the cathode (negative electrode) are respectively electrically connected to the anode and cathode of the current source by electrical conductors. Either the anode or the cathode is arranged within the drug reservoir, depending on the charge of the ionized drug, and is designated the active electrode. The other electrode is arranged within the return reservoir, and is designated the return electrode.
When current from the current source is supplied to the active electrode, the drug ions migrate from the drug gel in the reservoir toward and through the skin of the patient. At the same time, ions flow from the patient's skin into the saline solution of the return reservoir. Charge is transferred into the return electrode and back to the current source, completing the iontophoretic circuit. The electronic controller controls the current source so that drug delivery is accomplished at a constant or varying rate, or over a short, long or periodic time interval. This controller generally requires relatively complex electrical circuitry, and may include a microprocessor, to meet the current delivery requirements.
A single electronic controller and patch is suitable for the delivery of a single drug to the patient. When multiple drugs are to be delivered simultaneously, and those drugs can be delivered safely together, multiple patches, each patch containing a separate drug, may be used with respective multiple controllers.
In certain cases, however, the administration of different drugs from multiple patches simultaneously may be contraindicated. In other cases, the simultaneous administration of different drugs may be required to attain a desired therapeutic effect or to counteract an undesirable side effect. In either case, coordination among the multiple patches is required when delivering different drugs.
In addition, multiple patches may also be used to deliver a single drug from multiple sites on a patient's body. This would be advantageous, for example, when the current needed to deliver the desired drug dosage from a single patch would be high enough to cause discomfort to the patient. In this case, it would be desirable to deliver the drug from multiple patches, using a smaller dosage and thus a lower current at each patch. When multiple patches are used to deliver a single drug, it becomes important to coordinate the delivery from each patch to achieve the overall desired dosage.
Multiple patches may also be needed to deliver uninterruptedly a controlled drug dosage, for example, when the drug is needed for a life sustaining function. In this case, multiple patches are required because failure of a single patch would interrupt the delivery of the drug. By coordinating delivery of the drug from multiple patches, a failure at any one patch could be compensated for by increasing the current (and thus the drug dosage) of the other operative patches.
In all of the above cases, the delivery of a single drug or multiple drugs from multiple patches must be coordinated.
Existing independent electronic controllers, however, do not have the capability of providing this coordination.